In order to immunologically correct aberrant regulation of lymphopoiesis which leads to cancers such as lymphomas, myelomas, and leukemias, an understanding of normal regulatory events is needed. This investigation will study differentiation of functional lymphocytes from precursor cells of bone marrow origin. These properties will be correlated with biochemical and biophysical macromolecular membrane alterations. The experimental approaches will make use of an in vitro system to elucidate steps of maturation and the regulatory mechanisms which direct lymphoid precursor cell development into functional helper, effector, suppressor, and memory lymphocytes. Membrane-associated carbohydrates in glycolipid and glycoprotein states have been recently associated with functional properties of T cells. Events which trigger these changes will be studied along with other surface receptor and enzymatic changes. Selective maturation and induction of functional lymphocyte populations in vitro may eventually be used to repair immunodeficiencies or to provide appropriate numbers of antigen-specific lymphocytes that are capable of restricting growth of neoplastic tissue. Memory cells could be induced which supply back-up numbers of hyperactive effector or surveillant lymphocytes.